GemRB is a portable open-source implementation of the Infinity Engine
The ECE is for creation and managing ED3+ED4 characters.
Ur-Quan Masters High Definition
Provides a full suite of clients and servers for virtual worlds.
3D urban environment renderer : browser-app ; as well as a GTA clone
Role Playing Game Engine
Dice Roller
A tool for roleplaying gamemasters
Java Game, Simple 2d, for Practice and Examples
Damage calculator and items comparison tool for Diablo 3